1. Field of the Invention
The present invention relates generally to a method for controlling an internal combustion engine and, more specifically, to a method for determining a magnitude of knock in an engine and responding with corrective actions based on a cascading introduction of corrective techniques.
2. Description of the Prior Art
Engine knock occurs when fuel ignites prematurely within a combustion chamber of an engine. This can occur as a result of improper engine timing, the use of a fuel with an octane value that is too low, or other reasons. Those skilled in the art of engine control are well aware of various types of knock sensors and techniques to decrease knock by changing an engine operating variable. Typically, a knock sensor comprises an accelerometer that detects physical movement of the engine as a result of a knock event.
U.S. Pat. No. 5,215,058, which issued to Sakakibara et al. on Jun. 1, 1993, describes a knock control apparatus for internal combustion engines. The apparatus comprises a knock detecting unit, a knock intensity value detecting unit for detecting a knock intensity value from a knock detecting output signal of the knock detecting unit within a predetermined crank angle range, a unit for calculating a mean value of the knock intensity value, a unit for calculating a mean deviation between the knock intensity value and the mean value, a cumulative percentage point updating unit for updating a cumulative percentage point of the distribution of the knock intensity value, a first updated quantity calculating unit for calculating a first updated quantity based on the knock intensity value and the cumulative percentage point, a second updated quantity setting unit for setting a second updated quantity for updating the cumulative percentage point updating unit based on the magnitude relationship between the first updated quantity and the mean deviation.
U.S. Pat. No. 4,711,212, which issued to Haraguchi et al. on Dec. 8, 1987, describes an anti-knocking system for an internal combustion engine. The system is intended to prevent knocking in accordance with a knocking condition detected by a knock detecting apparatus on the basis of a distribution pattern of knock magnitude values derived from the output signal of a knock sensor. The knock detection apparatus is arranged to derive a knock magnitude value from the output signal of the knock sensor generated within a predetermined engine rotational angle at an interval thereby obtaining a plurality of knock magnitude values, determine a pattern of distribution of the plurality of the knock magnitude values on the basis of the results of comparison between the frequency that the knock magnitude value exceeds an upper threshold value and the frequency that the knock magnitude value goes below a lower threshold value.
U.S. Pat. No. 6,745,749, which issued to Unlund et al on Jun. 8, 2004, describes a method for adjusting adaptive program maps of an adaptive knock signal in an internal combustion engine and a method for adjusting the knock control in the engine. The method is intended for adjusting an adaptive characteristics map of an adaptive engine-knock control system and a method for adaptively controlling engine knock, the adaptive characteristics map being defined by at least one operating parameter, the adaptive characteristics map for each operating-parameter range being made up of a precontrol component that characterizes the ambient conditions, and a residual component that results from the engine-knock control, the value of the adaptive characteristics map for each operating-parameter range being given by the sum of the precontrol component corresponding to the specific operating-parameter range, and the residual component corresponding to the specific operating-parameter range.
U.S. Pat. No. 6,845,312, which issued to Cross et al on Jan. 18, 2005, discloses a method for detecting engine knock that includes a method for processing knock-related data which reduces the memory locations required for the method and also simplifies the processing steps needed to determine a sum, average, and threshold value relating to magnitudes of knock ratios. Inputs from either pressure sensors or accelerometers are filtered and then used to form a ratio between a knock portion of a curve and a reference portion. Sequential magnitudes of the knock ratio received and analyzed in a manner that reduces required memory locations and improves processing speed.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
It would be significantly beneficial if a method could be provided that responds to the occurrence of knock events in a way which allows the control methodology to be event driven, proportional, or a combination of both. In addition, it would be beneficial if such a method could also incorporate several different corrective techniques that can be applied in a cascading manner as a function of the cumulative knock history of a particular cylinder of an engine.